Can not execute middleware if using a exception handler? - clojure

Question

wrap-cors does not return access control headers when there is a bad request against my api endpoint. I believe this is because I am using a exception handler which might be blocking the middleware from running. I want to know how I can still execute the middleware for this route and append the cors headers to the response of bad requests.
exception handler
(defn- bad-request-handler
"Handles bad requests."
[f]
(f
(ring/response {:status "bad request"})))
app
(def app
(api
{:exceptions {:handlers
{::ex/request-validation (bad-request-handler response/bad-request)}}}
(POST "/" [] :body [item {(schema/required-key :item) schema/Bool}]
:middleware [#(wrap-cors % :access-control-allow-origin [#".*"]
:access-control-allow-methods [:post])]
:responses {200 {:description "ok"}
400 {:description "bad request"}} item)))

Answer 1

I've decided to append my own headers rather than using r0man/ring-cors.
I can determine the contents of the Access-Control-Allow-Methods by retrieving the :request-method value from the request.
However, this makes the assumption that the bad request handler will only ever be called by valid routes.
(defn- append-cors
"Allow requests from all origins"
[methods]
{"Access-Control-Allow-Origin" "*"
"Access-Control-Allow-Methods" methods})
(defn- bad-request-handler
"Handles bad requests."
[f]
(fn [^Exception e data request]
(->
(f request)
(update-in [:headers] merge (->
(request :request-method)
(name)
(clojure.string/upper-case)
(append-cors)))
(assoc :body {:status "bad request"}))))
I'm still not really sure why the cors headers are only added when the request is allowed.